JPH07173621A - Sintered target material for sputtering capable of high-speed film formation - Google Patents

Abstract

PURPOSE:To prevent the cracking of a target material even when sputtering power density is increased and carry out high-speed film formation by limiting the content of alkali metallic impurities in an oxygen-deficient sintered target material. CONSTITUTION:Compds. of Ba, Sr an Ti as constituent elements of BSTO are separately purified by recrystallization, distillation, sublimation or other method and the resultant high purity compds. are mixed in a specific ratio and sintered by firing in a flow of gaseous nitrogen to obtain the objective oxygen-deficient sintered target material for sputtering for forming a thin BSTO film represented by the general formula BaxSr1-xTiO3-y. The amt. of alkali metallic impurities in this target material is limited to <=100ppm and cracking is inhibited at the time of applying high output.

Description

Detailed Description of the Invention

[0001]

This invention relates to SrTiO ₃ and BaT
The present invention relates to a sintering target material used for forming a BSTO thin film represented by a composition formula of iO ₃ and (Sr, Ba) TiO ₃ by a sputtering method.

[0002]

2. Description of the Related Art Conventionally, infrared sensors and piezoelectrics are generally used.
Filter, piezoelectric vibrator, laser modulator, optical shutter
Components, semiconductor memory, thin film capacitors, etc.
As a base, SrTiO₃, BaTiO₃, And (S
r, Ba) TiO₃BSTO thin film represented by the composition formula
It is well known that it is used. Well
In addition, the above BSTO thin film is formed by the sputtering method.
The target material used to
The DC sputter phosphorus is formed by increasing the conductivity.
Film formation at high speed, and thus at high speed
Ba that can be done _XSr_1-XTiO_3-YRepresented by
It is also known that target materials are used.

[0003]

On the other hand, the recent advances in sputtering technology have enabled remarkable film formation at higher speeds, but the above general formula Ba _X Sr is used.
_{In the} case of a conventional sintered target having a composition of _1-X TiO _{3 -Y} (hereinafter referred to as an oxygen deficient sintered target), cracking is likely to occur when the applied output is increased in order to further increase the film formation rate. At present, it is impossible to form a film at a higher speed, and at present, only a film can be formed at a speed of about 15 nm / min.

[0004]

Therefore, from the viewpoints described above, the present inventors have focused their attention on the above-mentioned conventional oxygen-defect-type sintering target, and can use this to form a film at a higher speed. As a result of conducting a study to make it smooth, the conventional oxygen-defective sintering target described above has an alkali metal impurity content of 50%.
The content of the alkali metal impurities is reduced to 10 ppm or less, but the conductivity is further increased, and cracking occurs even when the film is formed by DC sputtering and high power application. That is, the research result was obtained that the film could be deposited at a high speed.
The present invention was made based on the above-mentioned research results, and has the general formula of Ba _X Sr _1-X TiO 2 having oxygen defects.
_{In the} sputtering sintered target material for BSTO thin film formation represented by _{3- Y} , alkali metal impurities of 10 pp
It is characterized in that the BSTO thin film can be formed at a high film forming rate by setting the thickness to m or less.

In the sintering target material for sputtering of the present invention, the content of alkali metal impurities is 1
Limited to 0 ppm or less, the content is 10 ppm
The reason is that the resistivity is constant in the range exceeding 10 .mu.m, but when it is less than 10 ppm, the resistivity starts to decrease and the cracking at the time of high output application is remarkably suppressed.

The sintered target material for sputtering according to the present invention comprises Ba, Sr, which is a constituent element of BSTO,
Each compound of Ti is highly purified by recrystallization, distillation, sublimation method, etc., and is mixed and fired so as to have a predetermined composition ratio.
Obtained by sintering.

[0007]

EXAMPLES Next, the sintering target material of the present invention will be specifically described by way of examples. Highly purified BaO and SrO powders were obtained by thermally decomposing highly purified Ba acetate and Sr acetate by the recrystallization method. Further, titanium tetraisopropoxide highly purified by the distillation method was dissolved in IPA, water was added to hydrolyze the mixture, and heat treatment was performed to obtain high purity TiO ₂ powder. These powders were mixed at a predetermined ratio and heat-treated to obtain BSTO powder having a perovskite type crystal structure. Further, this powder was heat-treated at 1200 ° C. for 2 hours in a nitrogen stream in order to form oxygen defects, and a conductive powder was obtained. Using this powder, sintered target materials for sputtering having a composition shown in Table 1 and having a diameter of 200 mm (hereinafter, referred to as target material of the present invention) 1 to 5 were prepared by using the powder.

For comparison purposes, commercially available BaO, SrO, and TiO ₂ powders were used as raw material powders and the sintering target materials for sputtering (hereinafter referred to as conventional target materials) 1 shown in Table 2 in the same manner as described above. ~ 5 were produced.
Alkali metal content of these target materials, sintered density,
The resistivity is shown in Table 3. Further, using these target materials, sputtering was performed under the conditions shown in Table 4 to form a film, and the film formation rate at this time was measured. The measurement results are shown in Table 5.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

[0013]

[Table 5]

[0014]

As described above, in the sintered target materials 1 to 5 of the present invention, even if the sputtering power density is increased, the target material does not crack, and higher speed film formation is possible. It is clear that the conventional target materials 1 to 5 are all cracked and cannot be put to practical use.

Claims (1)

[Claims] 1. A general formula Ba _X Sr _1-X Ti with oxygen defects.
In the sputtering sintering target material for BSTO thin film formation represented by O _3-Y , the amount of alkali metal impurities is set to 1
A sintered target material for sputtering capable of high-speed film formation, which has a content of 0 ppm or less.